Downhole well pump with bottom standoff

ABSTRACT

In a downhole well pumping system an elongated bottom standoff pipe member is connected at one end to the lower end of a well pump and includes a plug disposed at the opposite end of the standoff pipe. The standoff pipe member is adapted to rest on the wellbore bottom wall to relieve at least some of the tensile forces acting on and otherwise causing elastic stretching of the tubing string of the pumping system. The bottom standoff pipe member is preferably a smooth walled cylindrical member with fluid inlet ports and a gas relief port formed therein, respectively.

BACKGROUND OF THE INVENTION

In the operation of rod actuated reciprocating downhole well pumps, in certain applications, it is necessary or desirable to avoid using a tubing anchor in the wellbore at, above or, particularly, below the pump. Accordingly, in many applications of downhole well pumps, it is necessary to suspend the pump and the tubing string somewhat freely within the wellbore. This situation may result in substantial elastic elongation of the tubing string to which the pump is connected and the effective stroke of the pump is thereby reduced during operation to lift fluids out of the wellbore. Accordingly, there is a need to provide means to relieve at least part of the tension or suspension forces acting on the pump tubing string and the pump to reduce or eliminate elastic elongation of the tubing string when disposed in the wellbore and to also not hinder removal of the pump and tubing string from the wellbore when necessary or desirable to do so.

It is to overcome certain problems with prior art rod actuated reciprocating piston well pumping systems, including the problems described hereinabove, that the present invention has been developed.

SUMMARY OF THE INVENTION

The present invention provides an improved downhole well pumping system including, but not limited to, well pumping systems generally of the type described in my U.S. Pat. No. 6,135,203, issued Oct. 24, 2000.

In accordance with one aspect of the present invention a downhole well pump system is provided with a bottom standoff member, preferably a section of tube or pipe, engaged with the wellbore bottom wall to reduce or eliminate elastic stretching of the tubing string connected to the pump. The bottom standoff member is preferably, suitably connected directly to an elongated tubing or cylinder member comprising part of the downhole well pump and the standoff extends generally below the pump inlet. The standoff tubing or pipe member includes one or more openings provided therein for receiving fluids to be pumped by the downhole pump. The standoff tubing or pipe member also includes a port for relieving accumulations of gaseous fluids at or adjacent to the pump inlet.

In accordance with another aspect of the present invention a downhole well pump system is provided which includes a bottom standoff tubing or pipe member which is connected directly to the downhole well pump and which has a generally cylindrical shape and a smooth outer wall surface. The standoff member is preferably made of a suitable metal or plastic material, such as steel or polyvinylchloride (PVC), respectively.

Still further in accordance with the present invention, a well pumping system is provided which includes a downhole reciprocating piston type well pump and a pump bottom standoff tubing or pipe member extending below and connected to the pump cylinder, for example, and including a bottom plug part for engagement with the bottom of the wellbore and to allow the standoff to position the pump several feet above the bottom of the well to relieve tension on and stretching of the tubing string extending from the pump to the surface, and to minimize or eliminate penetration of the standoff member into the earth formation of the well bottom as a result of pump operation or the weight of the pump and tubing string.

Those skilled in the art will further appreciate the above mentioned features and advantages of the invention together with other important aspects thereof upon reading the detailed description which follows in conjunction with the drawing.

BRIEF DESCRIPTION OF THE DRAWINGS

The drawing FIGURE is a longitudinal central section view, in somewhat schematic form, of a downhole well pump system with a bottom standoff tubing or pipe member arrangement in accordance with the invention.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT

In the description which follows, like parts are marked throughout the specification and drawing with the same reference numerals, respectively. The drawing FIGURE may not be to scale and certain features may be shown in somewhat schematic or generalized form in the interest of clarity and conciseness.

Referring now to the drawing FIGURE, there is illustrated a portion of an earth formation 10 into which a wellbore 11 has penetrated and is lined with a casing 12 in a conventional manner. Casing 12 is suitably perforated at perforations 14 to allow fluids in the formation 12 to flow into the wellbore space, generally designated by the numeral 16. The wellbore space 16 is delimited by a bottom wall 17. A well pumping system 18 is disposed in the wellbore space and may be of the type described in my U.S. Pat. No. 6,135,203 issued Oct. 24, 2000. U.S. Pat. No. 6,135,203 is incorporated herein by reference.

The well pumping system 18 illustrated includes a downhole reciprocating piston well pump 20 generally of the type described in U.S. Pat. No. 6,135,203, including an elongated cylinder member 22, a standing valve 24 and a traveling valve 26 connected to a piston or plunger 28 on which a trash catcher 30 is mounted, as shown. Piston 28 is operably connected to an elongated actuating rod 31 for reciprocating motion to displace fluids from a chamber 32 upward through the tubing string 34 which is connected to cylinder member 22.

In order to properly locate the cylinder member 22 of pump 20 in wellbore 11 and to relieve at least some of the tension forces on and stretching of the tubing string 34 for in deep wells, for example, the invention contemplates the provision of an elongated standoff member comprising a tube or pipe 40 having a bottom plug 42 suitably secured thereto for engagement with the wellbore bottom wall 17. The standoff pipe member 40 is provided with a smooth, substantially constant diameter outer wall surface 44 to facilitate removal from the wellbore if solids accumulate around at least a lower portion of the standoff. Bottom standoff tube or pipe member 40 is also suitably secured to the pump 20 at a threaded connection 48, for example, between the standoff pipe member 40 and the cylinder member 22, as shown. Bottom standoff tube or pipe member 40 is provided with one or more elongated slots 50 therein, one shown, to allow fluids entering the wellbore space 16 to flow into an interior space 52 and flow through the pump 20 in response to actuation of same. Bottom standoff pipe member 40 is also advantageously provided with a gas relief hole or port 56 preferably disposed directly adjacent a fluid inlet port 25 of pump 20 to prevent accumulation of gas between the valve seat 58 and the chamber or space 52 which would prevent proper functioning of the pump 20 during reciprocation of the rod 30.

In operating a pump of the type described in U.S. Pat. No. 6,135,203 in water wells, for example, of depths of 200 to 600 feet, suspension of the pump system in the wellbore is usually suitable. However, in many applications of a pump of the type described in the above referenced patents, well depths of over one thousand feet may be encountered and the suspension forces on small diameter tubing, say tubing 34 having a diameter of about 1.00 inches to 3.0 inches, for example, may be substantial resulting in elastic stretching of the tubing and loss of effective pump stroke during pump operation. Moreover, if the lower end of the pump cylinder 22, or any type of anchor connected to the pump that adheres to the wellbore or the casing wall, becomes trapped or covered by sand or other particulate solids, retrieval of the pump from the wellbore may be difficult or impossible. The standoff member may be of any length necessary to perform its function and which length may be in a range of twenty feet to over one hundred feet, for example.

By providing a standoff tubing or pipe member, such as the standoff pipe 40 described and shown in the drawing, connected to the lower end of a downhole reciprocating piston well pump, such as the well pump 20, the pump may be lowered into the well sufficiently to reduce or eliminate elastic stretching of the tubing string and retrieval of the pump system from the wellbore, when needed, is enhanced.

In accordance with the invention, by providing a generally cylindrical smooth walled bottom standoff tube or pipe 40 connected to the well pumping system 18 and resting on the wellbore bottom wall 17, fluids may be allowed to flow into and through the slots or openings 50, one shown in the drawing, into the standoff interior chamber or space 52, for unrestricted flow through the pump 20 as it operates. Thus, the overall combination of structure as described and shown provides the advantages described above, as well others that will be apparent to those skilled in the art. The standoff tube or pipe member 40 may require to be only slightly larger in diameter than the maximum diameter of the well pumping system 18, including the cylinder 22, and may be formed of suitable materials, including plastics and metals, typically used for downhole well pumping systems.

The installation and use of the well pump system described hereinabove is believed to be understandable to those skilled in the art. Although a preferred embodiment has been described herein those skilled in the art will also recognize that various substitutions and modifications may be made without departing from the scope and spirit of the appended claims. 

1. In a downhole well pump system, the improvement comprising: a reciprocating piston pump connected to a tubing string and disposed in a wellbore, said pump including an elongated cylinder member; and an elongated standoff member connected to said cylinder member and adapted to engage a bottom wall of said wellbore for transferring at least a portion of the weight of said tubing string and pump to said wellbore bottom wall to reduce elastic stretching of said tubing string.
 2. The system set forth in claim 1 wherein: said standoff member comprises a cylindrical tube or pipe.
 3. The system set forth in claim 2 wherein: said standoff member includes a plug connected to a distal end thereof.
 4. The system set forth in claim 2 wherein: said standoff member includes at least one opening formed therein for admitting fluids from a wellbore space into a chamber defined by said standoff member.
 5. The system set forth in claim 2 wherein: said standoff member includes a gas relief port formed therein and providing an opening between said wellbore space and said chamber within said standoff member.
 6. The system set forth in claim 1 wherein: said standoff member is of a length of between about 20 feet and 500 feet.
 7. In a downhole well pump system, the improvement comprising: a reciprocating piston pump connected to a tubing string and disposed in a wellbore, said pump including an elongated cylinder member; and an elongated standoff pipe member connected to and extending below said pump, said standoff member including a plug connected to a distal end thereof for engagement with a well bottom wall.
 8. The system set forth in claim 7 wherein: said standoff member includes at least one opening formed therein for admitting fluids from a wellbore space into a chamber defined by said standoff member.
 9. The system set forth in claim 8 wherein: said standoff member includes a gas relief port formed therein and providing an opening between said wellbore space and said chamber.
 10. The system set forth in claim 7 wherein: said standoff member is of a length of between about 20 feet and 500 feet. 